Role of MR Imaging in Viral Encephalitis-A Clue Towards Aaetiological Agent

Abstract

Introduction: MRI plays a significant role in diagnosing viral encephalitis. It aids the diagnosis of causative agent, conditions mimicking the disease, identification of complications and hence prognostication of the patient. The present study analysed the MRI spectrum of different types of viral encephalitis and its role in diagnosing the causative virus. Aim: To study MRI findings of viral encephalitis and their correlation with CSF/biochemical/histopathological microbiological analysis. Materials and Methods: All patients suspected or previously diagnosed of CNS infections and referred to the department of Radiodiagnosis at Dayanand medical college and hospital, Ludhiana for imaging over a period of one and a half years were included in this study. Results: Most of the patients presented with fever and altered sensorium. CSF showed mildly raised proteins and pleocytosis. Asymmetric involvement of medial temporal lobes, cingulated gyri and insular cortices in herpes simplex infection was classical. Thalamic haemorrhages with/without basal ganglia and brainstem involvement were seen in dengue encephalitis and Japanese encephalitis. Diffusion restriction and haemorrhage were not seen in rhombencephalitis due to rabies. Varicella zoster vasculopathy involved both large and small vessels. Post viral demyelination [Acute Demyelinating Encephalomyelitis (ADEM)] mimicked viral encephalitis on MRI. An antecedent history of fever and response to steroids favoured the diagnosis of ADEM. Conclusion: We concluded that MRI is the modality of choice for diagnosing viral encephalitis and suggesting specific aetiological virus in an appropriate clinical and biochemical setting.

Keywords

• demyelination
• encephalitis
• hyperintense
• magnetic resonance imaging
• vasculopathy